Ferric dialkyl dithiocarbamates used to increase the vulcanization rate of monoolefin-non-conjugated diene terpolymers



United States Patent FERRIC DIALKYL DITHIOCARBAMATES USED TO INCREASE THE VULCANIZATION RATE OF MONOOLEFIN-NON-CONJUGATED DIENE TERPOLYMERS Victor S. Chambers, Naugatuck, Conn., assignor to Uniroyal, Inc., a corporation of New Jersey No Drawing. Filed May 27, 1964, Ser. No. 370,696 13 Claims. (Cl. 26023.7)

This invention relates to a method of vulcanizing unsaturated rubbery copolymers of monoolefins and to the vulcanizates obtained thereby. More particularly the invention relates to the sulfur cure of an interpolymer of at least two monoolefins and a copolymerizable diene, using as an accelerator a ferric dialkyldithiocarbamate in which the alkyl radical contains from 1 to 4 carbon atoms.

Unsaturated olefin copolymer rubbers such as ethylene-propylene-dicyclopentadiene terpolymer rubber prepared by solution polymerization with coordination-type catalysts have many desirable qualities, including the ability to be vulcanized with sulfur. However, it is unfortunate that the sulfur cure of such terpolymers is not as rapid as would be desired for some purpose, even when various known accelerators are employed. Thus, zinc dimethyldithiocarbamate for example does not produce a desirably high rate of sulfur cure of ethylene-propylenediene terpolymer, even through that accelerator is capable of producing an ample rate of cure in the more conconventional sulfur-curable rubbers. Even when zinc dimethyldithiocarbamate is used along with other accelerators such as mercaptobenzothiazole the sulfur cure of ethylenepropylene-diene terpolymer rubber is not as rapid as would be desired.

I am aware of such prior disclosures as those in US. Patents 1,386,153, 1,440,962, 1,440,963, 1,513,122, 2,283,- 334, 2,283,336, 2,303,593, 2,236,389 and 2,554,182 but nothing in those patents is suggestive of the present invention.

The present invention is based on the surprising dis covery that remarkably high rates of cure are obtainable in the sulfur cure of unsaturated olefin copolymer rubbers by using as an accelerator a ferric dialkyldithiocarbarnate of the structure:

where R and R area lkyl groups containing from 1 to 4 carbons which may be the same or different (methyl, ethyl, n-propyl, isopropyl, n-butyl, secondary-butyl, iso-butyl and tertiary butyl). This result is particularly unexpected in view of the fact that ferric dimethyldithiocarbamate does not similarly produce a rapid cure in the more conventional sulfur curable rubbers. The uniqueness of the present ferric dialkyldithiocarbamates is further attested to by the fact that numerous other metal dimethyldithiocarbamates, including the cadmium, cobaltous, nickel, cupric, mercuric, chromium (III), arsenic and antimony dimethyldithiocarbamates, do not produce the remarkable increase of speed made possible by ferric dialkyldithiocarbamate.

The sulfur-curable unsaturated elastomers to which the invention is applicable may be described as rubbery interpolyrners of at least two (e.g. three or more) alphamonoolefins (e.g., ethylene, propylene, butene-l, hexene- 1, 4-methylpentene-1, S-methylhexene-l, 4-ethylhexene-1, or similar olefins having the formula CHFCHR in which R is hydrogen or a hydrocarbon radical, particu- 3,330,790 Patented July 11, 1967 larly a saturated alkyl hydrocarbon radical having from 1 to 8 carbon atoms), and at least one (e.g., two or more) copolymerizable diene (ordinarily a non-conjugated diene) such as dicyclopentadiene, methylcyclopentadiene dimer, 1,4-hexadiene, 11-ethyl-1,11-tridecadiene, 1,9-octadecadiene, 1,5-cyclooctadiene', methylene norbornylene, or other suitable dienes such as are disclosed in British Patent 880,904, Dunlop Rubber Co., Oct. 25, 1961, US. Patents 2,933,480, Gresham and Hunt, Apr. 19, 1960, and 3,000,866, Tarney, Sept 19, 1961, and Belgian Patents 623,698 and 623,741, Montecatini Feb. 14, 1963; preferred are terpolymers of this kind containing from about 1 to about 25% (more preferably about 2 to about 15%) by weight of dicyclopentadiene or the like. Such sulfur vulcanizable unsaturated interpolymers will hereinafter he referred to as EPT elastomer.

In practicing the invention the EFT elastomer iscompounded with sulfur (or equivalent sulfur-yielding material) and the described ferric dialkyl dithiocarbamate accelerator. The vulcanizable composition of the invention further includes a long chain-fatty acid (e.g. C to C such as stearic acid, lauric acid, palmitic acid, oleic acid or equivalent acids and a metal oxide such as zinc oxide or the like. If desired these may be supplied in the form of a metal salt of a long-chain fatty acid, e.g., zinc stearate, zinc olcate, zinc laurate, and the like. A preferred form of the invention contemplates in addition a secondary accelerator, such as a thiazole or thiazole derivative, e.g., Z-mercaptobenzothiazole, metal salts of Z-mercaptobenzothiazole, e.g., the zinc salt, 2-benzothioazolyl disulfide, and Z-benzothiazolesulfenamides. The amounts of these ingredients are not critical and may be in accordance with conventional practice in the accelerated sulfur vulcanization of rubbers. It may be stated that in general the amounts of the ingredients will usually fall the following ranges:

Large quantities may be employed when it is desired to use the metal oxide as a filler.

However, larger or smaller quantities that those shown may be used if desired.

The vulcanizable composition of the invention in practice frequently contains other ingredients in addition. Thus, fillers are particularly useful, especially reinforcing fillers such as carbon black, silica, lignin, and the like. The filler may amount to from 0 to 500 parts or more per of EPT, preferably 0 to 300 parts. If desired the EPT-filler mix may be subjected to low hysteresis processing, for example by hot milling with conventional promoters, prior to compounding for vulcanization.

Oil extenders or similar plasticizers or softeners represent a particularly useful additional ingredient. Various oils, asphalts, resins and the like may be used for this The extender and/or filler (as well as the other ingredients) may be masterbatched, at least in part, in the solution or cement in which the elastomer is originally prepared, if desired, or these ingredients may be Banbury or mill mixed. Usually the zinc oxide, stearic acid, carbon black and softener oil are blended with the polymer in a Banbury and then the sulfur and accelerators added to this mix on a cool mill.

Various conventional antioxidants or similar auxiliary compounding ingredients may be included in the mix if desired.

The compounded EPT may be shaped in any suitable desired conventional manner such as molding, extruding, calendering, and the like, and it may if desired be combined with reinforcing structures such as fabric, wire, etc., for example in the manufacture of tires, footwear, coated fabrics, and the like.

In order to bring about the vulcanization, the mix is subjected to heat, ordinarily in a closed mold (although an open or oven cure may also be employed in appropriate cases). The vulcanization conditions may be the same as in conventional practice, although it will be understood that the invention permits a given level of cure to be attained more easily or more expeditiously than in conventional practice. The time and temperature of cure will of course vary with such factors as the degree of cure desired, the particular polymer employed, the amount of vulcanizing ingredients present, the size of the article, the character of the heating device, etc. The time and temperature of cure are in general inversely related. Usually satisfactory results are obtainable within a temperature range of from 250 to 400 F. and within time periods of from one minute to two or more hours.

Ferric dialkyldithiocarbamates may be made in known manner by adding an aqueous solution of ferric chloride to an aqueous solution of the sodium dialkyldithiocarbamate. A preferred practice involving the use of approximately 10% excess of the sodium dialkyldithiocarbamate as disclosed in British Patent 692,063 (5/27/ 1953) to Monsanto, gives a more stable ferric compound.

The following examples, in which all quantities are expressed by weight, will serve to illustrate the practice of the invention in more detail. The EPT used in the examples is an ethylene-propylene-dicyclopentadiene terpolymer containing 35-45% propylene and approximately 6% diene (calculated from the iodine number) with the balance being ethylene.

Example 1 This example describes the use of ferric dimethyldithiocarbamate as an accelerator and compares the cures obtained with it with those obtained with zinc dimethyldithiocarbamate or tetramethyl thiuram monosulfide are used. A masterbatch was prepared by mixing in a Banbury 100 parts of EPT having a Mooney viscosity of approximately 145, 50 parts of high abrasion furnace carbon black, 5 parts of zinc oxide, 1 part of stearic acid, and 25 parts of a naphthenic softener oil. Portions of this were then used to prepare the following stocks, the mixing being done on a mill heated at 120 F. (the amounts are all in parts by weight):

Ferric dimethyldithiocarbamate Zinc dimethyldithiocarbamatec 'Ietrarnethylthiuram monosulfide Mooney Scorch at 270 F.:

Scorch time, minutes Cure rate, minutes 4- These stocks were cured at 292 F. and 320 F. The results obtained are summarized in Table I below:

TABLE I Mins. Stock A Stock B Stock 0 Cured Cured at 292 F;

300% modulus, p.S.i 15 700 380 420 30 1,130 650 950 45 1, 350 980 1,180 Tensile, p.s.i 15 2,190 790 1, 220 30 2, 950 2,170 2, 980 45 3, 220 3,180 3, 380 Elongation, percent 15 635 505 655 30 535 675 615 45 535 615 570 Cured at 320 F.:

300% modulus p.s.i 5 450 240 220 10 900 580 640 15 1,130 880 890 Tensile, p.s.i 5 1, 720 820 490 10 3,200 2, 300 2, 850 15 3,100 3, 270 3, 200 Elongation, percent 5 670 620 615 10 635 685 700 15 540 650 610 Example 2 The procedure described in Example 1 was repeated except that the terpolymer used had a Mooney viscosity of approximately 60 rather than approximately as was the case in Example 1. The softener oil was omitted in the preparation of the masterbatch and the compounding was completed on a cool mill as follows:

Stock D M asterbatch Sulfur lvlercaptobenzothiazol Ferric dimethyldithiocarbamate. Tetramethylthiuram monosulfide Mooney viscosity of compounded stock Mooney scorch at 270 F.:

Scorch time, minutes Cure rate, minutes These stocks were cured at 320 F. and 400 F. The results are summarized in the table below:

TABLE 11 Mins. Stock D Stock E cured Cured at 320 F.:

300% modulus, p.s.i 5 640 390 Tensile, psi 5 1, 620 910 Elongation, percent 5 585 625 Cured at 400 F.:

300% modulus, p.s.i 1 650 420 Tensile, p.s.i 1 1, 690 810 Elongation, percent 1 600 540 These results show that the same rapid cure is obtained with ferric dimethyldithiocarbamate in a stock made from lower Mooney viscosity polymer and containing no extender oil.

Example 3 This example shows the effect on the rate of cure of varying the amount of ferric dimethyldithiocarbamate used in an EPT-black stock. A master batch was prepared These results show that ferric dimethyldithiocarbamate will give a satisfactory cure when used alone, but that the addition of 0.5 part of mercaptobenzothiazole improves the cure rate.

as described in Example 1 and portions of this were 5 Example 5 then used to prepare the following stocks, the mixing This example shows the effect of varying the amount of being done on a null heated to 120 F. zinc oxide. A masterbatch was prepared in a Banbury from 100 parts of EPT similar to that used in Example 1 having a Mooney viscosity of approximately 150-, 50 parts of high abrasion furnace black and 30 parts of a Stock F I G I H l I I I naphthenic type softener oil. This was then used to pre- U h h pare the following stocks the mixing being done on a raster atc 131 131 131 181 181 3 1.5 L 1.5 L5 L5 111111 at approxlmately 120 gglerqapdtpbeltlfiotldiialzlole-1?" 0.5 0.5 0.5 0.5 0.5

GU10 11119 y 1 1003.!" 8- mate 0.5 1.0 1.5 2.0 5.0 Stock N l O P Q R S Masterbatch 130 180 130 130 180 130 gm: oxidezf 5 1% Ii 2 1 none earie aci 1 Th t k d Th 1 Fern'edimethyldit 10- ese soc s were cure at F. e resu ts are carbamate L5 L5 L5 1 5 L5 given in the table below. Mereaptobenzothiazole 0.5 0.5 0.5 0.5 0.5 1.5 Sulfur 1.5 1.5 1.5 1.5 1.5 0.5 1.5

Portions of each of these were cured at 274 F., 292 D O o I Mim Stock stock Stock Stock stock 2:) F., 320 F., and 400 F. The results are summarlzed 1n cure F G H I J the table below:

300% modulus, p.s.i 5 220 350 490 590 440 10 328 Ming. StIoIck Stgek stlgck Stgek Stfick Stgck 15 8 1, cure Tensile, p.s.i 5 410 920 1,370 1,340 1,350

10 1,390 3,000 3,100 3,230 2,870 15 2,320 3,330 3,390 2,910 2,930 Cured at 274 F.: Elongation, percent 5 530 ego g; 03 520 01 6158115, 5.1 30 2,020 1,350 2,370 2,850 2,090

10 610 6 0 0 57 610 are a 15 040 040 550 400 530 Tensile, 1.51.-.. 15 2,500 2,400 2,430 2,530 2,430 120 Cured at 320 F.: Tensile, p.s.i. 7.5 3,100 3,100 3,100 3,000 2,920 190 Cured at 400 F.:

Tensile, .s.i. 2 3,000 3,550 3,470 3,000 2,870 345 These results show that a satisfactory cure can be ob- *NO cure tained with as little as 0.5 part of the ferric dimethyldithiocarbamate and that the optimum amount is approxi- 40 These data Show the benefit of Zme Oxldemately 1.5 to 2.0 parts. Example 6 ple 4 This example shows the benefit of using stearic acid This example shows the efiFect of using zero, 0.5, 1.0, Wlth e feme dunethyldlthleearbamate P mereapto' and 1.5 parts of mercaptobenzothiazole with the 1.5 parts benzethlazole aceeleraters an P elmllar to theft of ferric dimethyldithi'ocarbamate as the accelerator sysused 111 Example 1 having a M ney vlscoslty of approx1- tern.Amasterbatch was prepared as described in Example mately e e were PTePaYed desenbed the 1 and portions of this were mixed on a 120 F. mill to pretable below by m1X1I 1g the fi 5 mgoredlents m a Banbury Pare the following stocks and the rest on a m1ll at about 120 F.

Stock ..T|U|VIWX Y Stock 100 100 100 100 100 100 nil nil 0.2 0.? 1.0 1.2

5 5 5 gialsfterbatch 181 181 181 181 H i g h abr sion furnace Carbon 50 50 5O 50 50 50 u ur 1.5 1.5 1.5 1.5 ac Mercaptobenzothiazole None 0.5 1.0 1.5 Naphthenic type Softener oil--- 25 25 25 25 25 25 Ferric dimethyldithiocarbamate 1. 1.5 1.5 1.5 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 Mereaptobenzothiazole 0.5 0.5 0.5 0.5 0.5 0.5 Tetramethyl thiuram monosulfide 1.5 1.5 1.5 Fol-rig dimtethyldithio- 1 5 1 5 1 5 car ama e These stocks were cured at 320 F. The results are given in the table below.

Portions of these were cured at 320 F. The results of the tests are summarized in the table below.

Mins. Stock Stock Stock Stock Stock Stock cured T U V W X Y 300% modulus, 5 360 350 260 480 270 560 13.8.1. 7. 5 640 580 560 670 590 680 Tensile, p.s.i 5 980 1, 000 730 1, 850 800 2, 040 7. 5 2, 510 2,070 2, 390 2, 720 2, 310 2, 900 Elongation, 5 610 66 690 680 640 Percent. 7. 5 640 630 690 660 670 650 The results show that the ferric dimethyldithiocarbamate gives a faster cure than tetramethylthiuram monosulfide when the stock contains 0.5 or 1.0 part of stearic acid but not when no stearic acid is present.

8 Example 8 This example illustrates the use of ferric diethyl, di-n- Example 7 propyl, and di-n-butyldithiocarbamates and compares them with the corresponding zinc dithiocarbamates and This example shows that, in addition to mercaptobenzowith the ferric and zinc dimethyldithiocarbamates. A masthiazole, anumber of derivatives of mercaptobenzothiazole terbatch was prepared as described in Example 1 and are effective as secondary accelerators used with ferric portions of this were then used to prepare the following dimethyldithiocarbamate. A masterbatch was prepared in stocks, the mixing being done on a mill at 120 F.

Stock FF GG H11 11 JJ KK LL MM Masteibatch 181 181 181 181 181 181 181 181 Sulfur 1.5 Mercaptobenzothiazole 0. 5

Ferric dimethyl dithiocarbarnate. Zinc dimethyl dithiocarbamate.-- Ferric dietliyl ditliiocarbamate Zinc dicthyl dithiocarbamate Ferric di-n-propyl dithiocaibamate Zinc di-n-propyl dithiocarbarnate Ferric di-n-butyl dithiocarbamate- Zinc di-n-butyl dithiocarbama the same way as the one in Example 1 and portions of this were used to prepare the following stocks, the mixing being done on a mill at approximately 120 F.

These stocks were cured at 292 F. and 320 F. The results of the stress-strain tests are given in the following table.

Mins. Stock Stock Stock Stock Stock Stock Stock Stock cured FF GG HH II II KK LL MM Cured at 292 F.:

300% modulus, p.S.l i5 600 400 600 550 620 430 380 300 30 1, 200 720 1,150 1,150 900 900 780 650 45 1,780 1,080 1, 500 1, 500 1, 200 1, 120 1, 110 900 Tensile, 11.5.1 1, 680 750 1,800 1, 350 1, 500 1,110 940 700 3, 250 2, 240 3, 230 3, 130 2, 570 2, 430 2, 390 2, 200 2, 800 2, 950 3, 040 3, 240 3, 100 2, 690 3, 090 3,020 Elongation, Percent 15 590 600 610 560 460 630 590 30 550 600 560 590 590 550 610 530 45 440 530 450 500 550 490 550 620 Cured at 320 F;

300% modulus, rash. 5 400 300 380 340 400 300 260 200 i5 1, 150 1, 070 1, 180 990 980 800 750 700 Tensile, p.s.l 5 850 e00 530 700 980 550 570 390 15 3, 2, 700 3, 050 2, 950 2, 600 2, 300 2, 410 2, 330 Elongation, Percent 5 560 560 57 550 570 620 590 620 15 520 550 550 590 500 550 620 610 Smck Z AA BB CO DD EE These data show that with the diethyl, di-n-propyl, and 181 181 181 181 181 1 1 45 di-n-butyldithiocarbamates the advantage of the ferric f3 5 8 over the zinc compounds is still present, although less than bamate 1.5 1.5 1.5 1.5 1.5 1.5 with the ferric dimethyl versus the zinc dimethyldithiocar- Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 b t Mercaptobenzothiazole .t 0.5 Elma Zinc salt of mercaptobenzo- Example 9 thiq'lnln 0.5 "6 Benzothiazolyl disiilfide 5 v N-eyclohexyl-2-benzothiazole- 0 This example shows that the ferric and zinc di-methylfgi f i gsf g g g a dithiocarbamates are much superior to the ferric and zinc 1e 5u1f n mi 1e 0.5 morpholine carbodithioates as accelerators of the cure Portions of each of these were cured at 292 F. and 320 F. The results are summarized in the table below.

ins. Stock Stock Stock Stock Stock Stock cured Z AA B13 C 0 DD EE Cured at 292F.:

300% modulus, p.s.i 15 200 350 240 390 380 390 30 380 720 550 780 700 750 Tensile, p.s.i 15 450 1, 250 750 1, 300 1, 100 1,050 30 1, 350 2, 780 2, 2, 850 2, 540 2, 620 Elongation, Percent 15 605 630 650 635 610 610 30 635 635 670 635 625 640 Cured at 320 F.: 300% Modulus, p.5.i; 15 930 1, 180 1, 050 1, 170 1, 1, 090 Tensile, p.s.i 15 2, 807 3, 600 3, 520 3, 620 3, 210 8, 420 Elongation, Percen 15 61 610 620 600 580 600 These results show that all of these mercaptobenzothia- Zole derivatives possess activity as secondary accelerators for ferric dimethyldithiocarbamate and any one of them can be used with this dithiocarbamate to give the improved cure rate.

Example 1 with 50 parts of high abrasion furnace carbon black, 25 parts of a naphthenic type softener oil, 5 parts of zinc oxide, and 1 part of stearic acid. Portions of this 75 were then used to prepare the following stocks, the mixing being done on a mill at about 120 F.

These stocks were cured at 292 F. The results are summarized in the table below.

It is very evident from this data that the two morpholine carbodithioates are poor accelerators since very little cure was obtained in stocks NN and 00.

Example 10 This example shows the comparison of ferric dimethyldithiocarbarnate to the cobalt, nickel, eupric, mercuric, chromium, arsenic, and antimony dimethyldithiocarbamates as accelerators for EPT. A masterbatch was prepared in the same way as the one in Example 1 and portions of this were used to prepare the following stocks,

the mixing being done on a mill at approximately 120 F. 35

Stock RR SS TT celerators in such a stock. A masterbatch was prepared by mixing in a Banbury 100 parts of the same type of EPT elas-tomer as used in Example 1, 100 parts of white clay, 20 parts of titanium dioxide, 30 parts of the softener oil used in Example 1, 5 parts of zinc oxide and 1 part of stearic acid. Portions of this were then used to prepare the following stocks, the mixing being done on a mill at approximately 120 F.

$500k A1 B1 C1 Masterbatch 256 256 256 Sulfur 1. 5 1. 5 1 5 Mereaptobenzothiazole 0. 5 0. 5 0 5 Ferric dimethyldithioearbamate" 1. 5

Zinc dimethyldithiocarbamate. Tetramethylthiuram monosulfide. 1.5

These stocks were cured at 292 F. and 320 F. The results are given in the table below.

Mins. Stock Stock Stock cured A1 l 0r Cured at 292 F;

300% modulus, p.s.i 15 190 180 90 250 220 220 420 260 300 Tensile, p.s.i 15 300 190 100 30 940 420 500 45 890 700 840 Elongation, percent 15 880 775 810 30 860 940 925 45 675 925 875 30 Cured at 320 F.:

300% modulus, p.s.i 10 220 180 210 15 290 230 300 Tensile, p.s.i 10 640 390 480 15 970 660 870 Elongation, pereent .1 10 910 910 940 15 780 880 810 Masterbatoh Mercaptobenzothiazole. Sulfur Dimethyldithiocarbamate:

Mereurim C ln'ornium results are summarized in the following table.

These results show that in a clay loaded stock the ferric dimethyldithiocarbamate, used as the primary accelerator,

Mins. Stock Stock Stock Stock Stock Stock Stock Stock Stock cured RR SS TT UU W WW XX YY ZZ Cured at 292 F;

300% modulus, p.s.i 15 180 220 220 390 460 700 380 30 250 640 560 820 710 1, 180 650 Tensile, p.s.i 15 220 390 540 790 l, 180 2, 190 790 30 590 1, 980 1, 980 2, 240 2, 180 2, 950 2, 170 Elongation, percent 15 640 575 640 575 635 595 30 635 640 685 590 605 535 675 Cured at 320 F;

300% modulus, p.s.i 5 40 300 290 460 240 10 40 50 220 430 300 490 840 900 580 Tensile, p.s.i 5 50 100 190 230 390 820 810 1, 720 820 10 60 100 630 1, 420 1, 590 1,820 1, 970 3, 200 2, 300 Elongation, percent. 5 385 535 6 0 565 615 580 590 670 620 "No cure.

These data show that the ferric dimethyldithiocarbamate develops cure at a faster rate than any of the other dithiocarbamates.

Example 11 This example shows the effectiveness of ferric dimethyldithiocarbarnate as an accelerator in a non-black loaded stock and compares it with zinc dimethyldithiocarbamate and with tetramethylthiuram monosulfide as acwill develop a high tensile more rapidly than will zinc dimethyldithiocarbamate or tetramethylthiuram mono- Example 12 This example shows that ferric dimethyldithiocarbamate as the sole accelerator is more eifective than zinc dimethyldithiocarbamate. A masterbatch was prepared as described in Example 1 and portions of this were used to prepare the following stocks, the mixing being done on a mill at approximately 120 F.

12- The stocks were then cured at 320 F. The results of the stress-strain tests are given in the table below.

5 Mins. Stock Stock Stock Stock Stock .1, D1 E1 F1 G1 H1 l I1 cured T1 1 L1 M1 300 1I10tlLlluS,1l)S. s .in 3 200 200 700 330 lliifiifffitfii'"""iiijiiiii: 1 if; ii; iii if; if I q 5 no 3 1,100 30 Ferricflimethymitllwcmbamate- 0375 Tensile lbs M in g 2 25 {Q38 1 Zinc dlmetllyldlthlocalbamate 0.15 1. 1 5 31500 2:980 5: 21450 7.5 3, 040 3,500 3,100 2,050 Elongation, percent 3 1,000 1,000 770 8540 5 370 000 500 770 7.5 730 700 530 700 These stocks were cured at 292 F. The results of the stress-strain tests are given in the following table.

These results show that in stocks prepared from terpolymers containing dienes other than dicyclopentadiene, namely 1,4-hexadiene or methylene norbornylene, ferric Hills. Stock Stock Stock Stock Stock Stock cured D1 E1 Fl G1 H1 11 d lmethyldlthloc arbamate glves a faster cure than does Zinc dlmethyldlthlocarbamate.

300% modulus, 15 100 100 230 130 120 100 Example 14 28 38 $88 328 38 338 23 I 15 500 490 690 290 220 Inorder to determine the effect of stearlc acid on the Tensile, .s.1- 30 1,530 1,530 1,300 1,130 1,030 1,050 actlvlty of the two accelerators ferric and zinc dlmethyl- 00 3,100 3,040 2,020 2,350 2,300 2,700 dithiocarbamate a series of tests were run using 0 01 E1 11 ation, 15 035 030 035 050 000 750 ger cent 005 070 055 090 030 715 0.5, 1.0, and 2.0 parts of stearlc acld (uslng the EPT 655 680 680 composition of Example 1). It was found that when less than 1.0 part of stearic acid was used raw the ferric 30 compound was less active than the zinc compound but when 1.0 or 2.0 parts were used the ferric compound These data show that satisfactory cures can be ob was definitely superior. To show this the tensiles of the tained with stocks containing no thiazole, and that the cures at 320 F. are tabulated below.

Mins Nil Nil 0.1 0.1 0.5 0.5 1.0 1.0 2.0 2.0 cured Zn Fe Zn Fe Z11 Fe Zll Fe Zn Fe ferric dimethyldithiocarbamate is better than the zinc di- It appears that the stearic acid activates the ferric dimethyldithiocarbamate over a range of concentrations. methyldithiocarbamate while retarding the zinc dithiocar- E Y a m pl e 13 bamate. It should be noted that in this series the best that 50 the zinc compound could do is still short of the results The EFT used the Qther eXZ1II1l91S ba$ been the one with the ferric compound with 1.0 stearic acid. Contalnlflg dlcydopentadlene as the dlene- The Present Having thus described my invention, what I claim and example illustrates the use of an EPT made wlth 1,4- d i to protect b L tt P t 11 hexadiene as the diene monomer, and another EPT made 1 A h d of curing n t t d rubbery copolymer With Fl y nol'bomylene- A masterbatch a made of ethylene, a different alpha-monoolefin, and at least one y IIllXlIlg 1n the l y Parts of 1,4-he.Xad1ene copolymerizable non-conjugated diene, said copolymer P 5 Parts of Zlnc OXlde, 50 Parts f hlgh abraslon containing from 1 to 25% by weight of said diene, com furnace black, and 20 Parts of naphthemc yp Softener prising subjecting .to vulcanizing conditions a composition .oil. A second masterbatch was prepared except that 100 comprising the said copolymer, sulfur, a ferric dialkyl- Parts Of methylene norbomylene EPT Weffi useddithiocarbamate in which the alkyl groups contain 1 to i ns f each of these were then Used f P P F Stocks 4 carbon atoms as a primary accelerator, zinc oxide, a according to the following table, the mlxmg b61113 done fatty acid having from 10 to 20 carbon atoms, and, as a on a mill at approximately 120 F. secondary accelerator, a thiazole selected from the group consisting of Z-mercaptobenzothiazole, zinc salt of 2-mercaptobenzothiazole, 2-benzothiazolyl disulfide, and 2- benzothiazolesulfenamides, the proportions of said ingre- Stock J, L1 dients being, by weight, per parts of said copolymer: 0.1 .to 10 parts of sulfur, 0.5 to 5 parts of ferric dlalkylmasterbatch (13416351116113 T 130 dlthlocarbflmatez to 5 Parts of fatty a to 5 Masiorbatcll #2 (methylene nor- 70 parts of zlnc mode, and up to 2 parts of thlazole accelerbornylene EPT) 180 t smile Acld 1. 1.0 1.0 a s uliur 1 2. A method of curing unsaturated rubbery terpolymer Fgi r iii diiiizi l iii l(l01110051055151e. 1:5 115 of ethylene, a dlfiernt P 9 and a Zinc dimetllyldithiocarbamate 1- 5 polymerlzable non-con ugated dlerle, said terpolymer con- 75 taining from 2 to 15% by weight of said diene, comprising subjecting to vulcanizing conditions a composition comprising the said terpolymer, sulfur, a ferric dialkyldithiocarbamate in which the alkyl groups contain 1 to 4 carbon atoms as a primary accelerator, zinc oxide, stearic acid, and, as a secondary accelerator, a thiazole selected from the group consisting of Z-mercaptobenzothiazole, zinc salt of Z-mercaptobenzothiazole, 2-benzothiazolyl disulfide and 2-benzothiazolesulfenamides, the proportions of said ingredients being, by weight, per 100 parts of said terpolymer: 0.1 to 10 parts of sulfur, 0.5 to parts of ferric dialkyldithiocarbamate, 1.0 to 5 parts of stearic acid, 0.2 to 5 parts of zinc oxide, and up to 2 parts of thiazole accelerator.

3. A method comprising heating at a temperature of 250 to 400 F. for 1 minute to 2 hours a composition comprising, by weight, 100 parts unsaturated rubbery terpolymer of ethylene, propylene and a copolymerizable non-conjugated diene, the said terpolymer containing from 2 to 15% by weight of said diene, 0.1 to 5 parts of a ferric dialkyldithiocarbamate in which the alkyl groups contain from 1 to 4 carbon atoms, 0.1 to parts sulfur, 1.0 to 5 parts stearic acid, 0.2 to 5 parts zinc oxide, and up to 2 parts of a thiazole accelerator selected from the group consisting of 2-mercaptobenzothiazole, zinc salt of 2-mercaptobenzothiazole, 2-benzothiazolyl disulfide and 2- benzothiazolesulfenamides.

4. A method as in claim 3 in which the said alkyl group is methyl.

5. Amethod as in claim 3 in which the said alkyl group is ethyl.

6. A vulcanizable composition comprising unsaturated ethylene-propylene-copolymerizable diene rubber the said diene being non-conjugated and being present in the rubber in amount of from 2 to by weight of the rubber, sulfur, a ferric dialkyldithiocarbamate in which the alkyl group contains 1 to 4 carbon atoms, stearic acid, zinc oxide, and, as a secondary accelerator, a thiazole selected from the group consisting of Z-mercaptobenzothiazole, zinc salt of Z-mercaptobenzothiazole, 2-benzothiazolyl disulfide and 2-benzothiazolesulfenamides, the proportions of said ingredients being, by Weight, per 100 parts of said rubber: 0.1 to 10 parts of sulfur, 0.1 to 5 parts of ferric dialkyldithiocarbamate, 1.0 to 5 parts of stearic acid, 0.2 to 5 parts of zinc oxide, and up to 2 parts of thiazole accelerator.

7. A vulcanizable composition comprising unsaturated ethylene-propylene-dicyclopentadiene terpolymer rubber containing from 2 to 15% by weight of dicyclopentadiene, sulfur, a ferric dialkyldithiocarbamate in which the alkyl group contains 1 to 4 carbon atoms, stearic acid, zinc oxide, and a thiazole accelerator selected from the group consisting of Z-mercaptobenzothiazole, zinc salt of 2- mercaptobenzothiazole, Z-benzothiazolyl disulfide, and 2- benzothiazole-sulfenarnides, the proportions of said ingredients being, by weight, per 100 parts of said rubber: 0.1 to 10 parts of sulfur, 0.1 to 5 parts of ferric dialkyldithiocarbamate, 1.0 to 5 parts of stearic acid, 0.2 to 5 parts of zinc oxide, and up to 2 parts of thiazole accelerator.

8. A vulcanizate derived from a composition comprising unsaturated ethylene-propylene-copolymerizable diene rubber the said diene being non-conjugated and being present in the rubber in amount of from 2 to 15 by weight of the rubber, sulfur, a ferric dialkyldithiocarbamate in which the alkyl group contains 1 to 4 carbon atoms, stearic acid, zinc oxide, and, as a secondary accelerator, a thiazole selected from the group consisting of Z-mercaptobenzothiazole, zinc salt of Z-mercaptobenzothiazole, 2-benzothiazolyl disulfide and Z-benzothiazolesulfenamides, the proportions of said ingredients being, by weight, per 100 parts of said rubber: 0.1 to 10 parts of sulfur, 0.1 to 5 parts of ferric dialkyldithiocarbamate, 1.0 to 5 parts of stearic acid, 0.2 to 5 parts of zinc oxide, and up to 2 parts of thiazole accelerator.

9. A vulcanizate as in claim 8 in which the rubber is a copolymer of ethylene, propylene and dicyclopentadiene.

10. A vulcanizate as in claim 8 in which the rubber is a copolymer of ethylene, propylene and 1,4-hexadiene.

11. A vulcanizate as in claim 8 in which the rubber is a copolymer of ethylene, propylene and methylene norbornylene.

12. A vulcanizate as in claim 8 inwhich the said alkyl group is methyl.

13. A vulcanizate as in claim 8 in which the said alkyl group is ethyl.

References Cited UNITED STATES PATENTS 2,283,336 5/1942 Neal et al 260786 2,631,984 3/1953 Crawford et a1 260-] 2,933,480 4/1960 Gresham et al 26080.5 3,000,866 9/1961 Tarney 260-795 3,023,195 2/1962 Martin et a1. 26079.5 3,093,620 6/1963 Gladding et a1. 26079.5 3,093,621 6/1963 Gladding 26079.5 3,278,480 10/1966 Radcliif et a1. 26041 FOREIGN PATENTS 33/5434 1958 Japan.

OTHER REFERENCES Wolf et al.: India Rubber World, May 1949, p. 191.

DONALD E. CZAJA, Primary Examiner. LEON J. BERCOVIT Z, Examiner. R. A. WHITE, Assistant Examiner, 

1. A METHOD OF CURING UNSATURATED RUBBERY COPOLYMER OF ETHYLENE, A DIFFERENT ALPHA-MONOOLEFIN, AND AT LEAST ONE COPOLYMERIZABLE NON-CONJUGATED DIENE, SAID COPOLYMER CONTAINING FROM 1 TO 25% BY WEIGHT OF SAID DIENE, COMPRISING SUBJECTING TO VULCANIZING CONDITIONS A COMPOSITION COMPRISING THE SAID COPOLYMER, SULFUR, A FERRIC DIALKYLDITHIOCARBAMATE IN WHICH THE ALKYL GROUPS CONTAIN 1 TO 4 CARBON ATOMS AS A PRIMARY ACCELERATOR, ZINC OXIDE, A FATTY ACID HAVING FROM 10 TO 20 CARBON ATOMS, AND, AS A SECONDARY ACCELERATOR, A THIAZOLE SELECTED FROM THE GROUP CONSISTING OF 2-MERCAPTOBENZOTHIAZOLE, ZINC SALT OF 2-MERCAPTOBENZOTHIAZOLE, 2-BENZOTHIAZOLYL DISULFIDE, AND 2BENZOTHIAZOLESULFENAMIDES, THE PROPORTIONS OF SAID INGREDIENTS BEING, BY WEIGHT, PER 100 PARTS OF SAID COPOLYMER: 0.1 TO 10 PARTS OF SULFUR, 0.5 TO 5 PARTS OF FERRIC DIALKYLDITHIOCARBAMATE, 1.0 TO 5 PARTS OF FATTY ACID, 0.2 TO 5 PARTS OF ZINC OXIDE, AND UP TO 2 PARTS OF THIAZOLE ACCELERATOR. 